The supreme body of the Baltic Assembly is the Session. The Session is empowered to make decisions if more than half of the members of each national delegation are present.

There are ordinary and extraordinary Sessions. The ordinary Session is convened once a year, according to a yearly rotation principle of the presidency in Estonia, Latvia and Lithuania. Before 2003, there were two Sessions a year – in spring and autumn, and countries - participants had half a year presidency.

Decisions of the Baltic Assembly are adopted by voting. Each national delegation has one vote. A decision is adopted if all the national delegations have voted in favour of it.

Any national delegation may propose to organise an extraordinary session. On 8-9 February 1998 in Helsinki, Finland, following to the 2nd Joint Meeting of the Nordic Council and the Baltic Assembly, the first extraordinary Session of the Baltic Assembly took place. The second extraordinary Session of the Baltic Assembly was held on 27-29 April 2005 in Pärnu, Estonia, within framework of the 5th Joint Meeting of the Baltic Assembly and the Nordic Council.

The Baltic Assembly has held 38 Sessions. The latest, 38th Session of the Baltic Assembly, was held on 28-29 November 2019 in Riga, Latvia. The next Session will take place on 5-6 November 2020 in Tallinn, Estonia.